/diy/ - Do It Yourself

I'm renovating a room in my house the didn't have a ceiling light fixture, and I've run into a problem with the wiring, I'm hoping someone here can help out.

There's an outlet in the room that has two lines of electrical wiring going into the box. One of these is connected to a light switch, the other is not.

I started by disconnecting the outlet from the light switch wire (call it line A) and connecting it to the non-light switch wire (line B). At this point the outlet works and is not affected by the light switch.

Then I put together the light fixture and was able to get it to turn on by plugging the bare wires into the outlet (just so I knew it worked) but when I connect it to line A it does not turn on. However I know that there is electricity running through line A, because it works when connected to the outlet.

Pic related, line A connected to the light fixture.

Thanks in advance